This invention relates to a process for the absorption of sulfur compounds, especially H.sub.2 S, from hydrocarbon- and/or CO.sub.2 -containing gases by scrubbing with a physical solvent, and then regenerating and reusing the solvent.
A process step frequently necessary in the processing of raw gas streams is the separation of sulfur compounds, e.g., H.sub.2 S, COS, CS.sub.2, and mercaptans as well as metallic sulfides in some cases. Among these impurities, which generally must be kept away from downstream stages due to their corrosive and catalyst-damaging properties or for other reasons, H.sub.2 S is found most frequently in such gas streams, and is generally the predominant impurity.
Examples of gaseous streams that require sulfur compound removal include but are not limited to natural gases, refinery gases, coke oven gases, gases from coal refining, and hydrogen-containing gaseous mixtures. The sulfur compounds are separated from these gaseous streams preferably by a gas scrubbing step with, in particular, a physical solvent (for additional details, see "Erdoel-Kohle-Erdgas-Petrochemic vereinigt mit Brennstoffchemie" (Petroleum-Coal-Natural Gas-Petrochemistry Combined with Fuel Chemistry) vol. 35, issue 8, August 1982 pp. 380-385), incorporated by reference herein. The absorbents employed in that process dissolve the sulfur compounds without chemical reaction and can be desorbed of these sulfur and compounds by expansion and/or stripping.
It has been found, however, that the use of physical scrubbing processes for the desulfurization of gases containing C.sub.3+ hydrocarbons is normally greatly impeded by coabsorption of these hydrocarbons. The reason for this is that C.sub.3 and also C.sub.4 hydrocarbons remain at least partially in the H.sub.2 S during regeneration of the solvent and the separation of such hydrocarbons from the H.sub.2 S is prohibitively expensive. The hydrocarbons in the H.sub.2 S not only represent a loss, but they are also technically undesirable in the follow-on Claus plants for the further processing of H.sub.2 S.